aarch64: allow reading system control register when halted in EL0

There's no access to system control register in EL0. Circumvent by
moving the PE to EL1 before reading, and switch back to original mode
afterwards.

Change-Id: I309f4eea5597ffc88fc892e9bbb826982e8a44ec
Signed-off-by: Matthias Welwarsky <matthias.welwarsky@sysgo.com>

diff --git a/src/target/aarch64.c b/src/target/aarch64.c
index 3510db23503a31c52f6414e962db69063b625957..41bea2e93dca22531055a6d25004f86039e966cd 100644 (file)
--- a/src/target/aarch64.c
+++ b/src/target/aarch64.c
@@ -698,6 +698,8 @@ static int aarch64_post_debug_entry(struct target *target)
 
        switch (armv8->arm.core_mode) {
                case ARMV8_64_EL0T:
+                       dpmv8_modeswitch(&armv8->dpm, ARMV8_64_EL1T);
+                       /* fall through */
                case ARMV8_64_EL1T:
                case ARMV8_64_EL1H:
                        retval = armv8->arm.mrs(target, 3, /*op 0*/
@@ -725,13 +727,20 @@ static int aarch64_post_debug_entry(struct target *target)
                        if (retval != ERROR_OK)
                                return retval;
                break;
-               default:
+
+               case ARM_MODE_SVC:
                        retval = armv8->arm.mrc(target, 15, 0, 0, 1, 0, &aarch64->system_control_reg);
                        if (retval != ERROR_OK)
                                return retval;
                        break;
+
+               default:
+                       LOG_INFO("cannot read system control register in this mode");
+                       break;
        }
 
+       dpmv8_modeswitch(&armv8->dpm, ARM_MODE_ANY);
+
        LOG_DEBUG("System_register: %8.8" PRIx32, aarch64->system_control_reg);
        aarch64->system_control_reg_curr = aarch64->system_control_reg;